We propose to develop an experimental mouse lymphoma system which may be used to test the use of age cohort variation hypothesis on the selection and monitoring of therapy at different times during tumor growth. Studies proposed for the coming year: a. Continuing investigation of the age cohort variation and chemotherapeutic sensitivity of C57BL ascitic lymphomatous tumors to a variety of chemotherapeutic agents. b. Reappearance in chemo-sensitivity induced by therapeutic agents following tumor transplantation. We are particularly interested in advanced tumors and means of stimulating proliferative activity in the advanced tumor. Further study of the alkylating agents, nitrogen mustard, BCNU, cytoxan, which are cycle-non-specific chemotherapeutic agents, which show activities against actively proliferating or non- proliferating tumors and may represent means of causing reproliferative activity. c. We hope to perform some radiobiological studies in the coming year on the radiation sensitivities of varying age-cohort tumors. d. Flow-micro Fluormetric studies of DNA per cell content during tumor growth and tumor therapy. We are expecting to cooperate with the Los Alamos Scientific Laboratory group in order to study samples of our tumor, the LSA lymphoma, in an effort to further extend our observation on the age cohort composition of tumors during tumor growth by standard chemical and isotope analysis. It is expected that we will study the tumor in ascites form growing in the peritoneal cavity, subcutaneously as a solid tumor, in viscera such as the liver and spleen and other sites. A supplemental project grant is proposed and support requested as part of this renewal request. The project will study Age Cohort problems for a solid EMT6 mammary tumor of Balb/c mice.